These could use a range.

Classifieds: http://backpack.tf/classifieds/search/stereo

One for 1.55, two for 1.66

Selling:

http://www.tf2outpost.com/trade/11891834 1.33, sold

http://www.tf2outpost.com/trade/11890553 1.55, had an offer of pocket purrer (1.66)

http://www.tf2outpost.com/trade/11884519 1.33

http://www.tf2outpost.com/trade/11877274 1.33, any scout hat or S.Knife, sold

http://tf2tp.com/trade.php?trade=9551296 1.33

http://www.tf2outpost.com/trade/11056555 Got offered 1.66

http://www.tf2outpost.com/trade/11893440 1.11

http://www.tf2outpost.com/trade/11884172 bp.tf price, sold

http://www.tf2outpost.com/trade/11845442 Offer of medi-mask (1.66-2 ref)

Unsold:

http://www.tf2outpost.com/trade/11896551 1.66

http://www.tf2outpost.com/trade/11842072 1.66

http://www.tf2outpost.com/trade/11800018 bp.tf high price

http://www.tf2outpost.com/trade/11784894 1.66, willing to sell for 1.55, got offered 1.44

http://www.tf2outpost.com/trade/11776350 high bp.tf price, rejected 1.44

http://www.tf2outpost.com/trade/11854356 1.66

http://www.tf2outpost.com/trade/11860541 1.66

http://www.tf2outpost.com/trade/11868423 1.66

Buying:

http://www.tf2outpost.com/trade/11815432 1.44

http://www.tf2outpost.com/trade/11898753 Soviet Gentleman (1.33-1.66) + S.Skulcutter (0.11)

http://www.tf2outpost.com/trade/11890866 1.66, willing seller

http://www.tf2outpost.com/trade/11654643 1.33, bought one

http://www.tf2outpost.com/trade/11786208 1.66, two willing sellers

http://www.tf2outpost.com/trade/10622067 1.33, 6 adds for shades

I'll try to find more proof supporting low end. If you have some reflections/proofs, post it below.